1. Field of the Invention
The present invention relates to safety ski bindings which are adapted to lock the toe end of a ski boot in position so as to constitute a toe abutment device.
In more precise terms, the invention relates to toe abutment devices of the so-called "multidirectional-trip" type comprising a boot-retaining jaw unit mounted for pivotal displacement in different directions, a resilient retaining mechanism being provided for maintaining the jaw unit in its normal position.
Thus, in the event of a torsional stress exerted on the skier's foot, the jaw unit is capable of lateral displacement in order to permit disengagement of the ski boot. However, the jaw unit is also capable of upward displacement so as to permit disengagement of the ski boot in this direction in the event of a backwardfall movement of the skier. It may be added that, in some types of toe abutment device, the jaw unit is mounted so as to be capable of displacement in all directions in order to disengage the ski boot under optimum conditions in the event of a complex fall that is to say, a falling movement in which a twisting effort is combined with an upward extension effort or else in the event of a backward fall accompanies by a twisting effort.
2. Description of the Prior Art
In order to achieve a satisfactory standard of safety, certain types of toe-binding abutment devices are so designed that a forward thrust exerted on the ski boot and caused by an incipient forward fall, for example, produces a reduction in the elastic resistance acting in opposition to rotational displacement of the body of the corresponding toe-abutment device. In point of fact, this forward thrust has the effect of increasing the friction forces set up by the ski boot and consequently of increasing the stiffness of ski-boot release. It is therefore necessary to reduce the elastic resistance of the boot-retaining mechanism in order to ensure that the magnitude of the retaining force remains substantially the same.
Thus, French Pat. No. 2,395,046 describes a toe-abutment device in which the boot-retaining jaw unit is mounted for axial sliding motion on the rotary body of the jaw unit in such a manner as to produce a reduction in torsional elastic resistance in the event that a thrust is exerted on said jaw unit in the forward direction. The resilient mechanism provided in this abutment device consists of a piston which is housed within the rotary body and is applied by a spring against a flat face formed on the pivot of said rotary body. The piston is adapted to carry two lateral extensions placed on each side of the pivot, and the boot-retaining jaw unit is intended to produce action on the ends of the extensions in the event of forward displacement of the unit. This accordingly has the effect of moving the piston away from the flat face which normally serves as a bearing surface for the piston and thus of permitting free rotational displacement of the abutment body.
In the event of a forward fall, the ski boot is therefore completely released. However, such an abrupt release constitutes a potential hazard. Furthermore, the toe-abutment device described in the cited patent does not in any way permit release of the ski boot in the event of a backward fall. A fortiori, no arrangements are therefore made to reduce elastic resistance to rotational displacement in the event of a backward fall.
French Pat. No. 2,439,601 describes a ski binding which can constitute both a heel-holding device and a toe-abutment device. This ski binding is so designed as to permit upward release of the corresponding end of the ski boot, which is not the case with the toe-abutment device mentioned earlier. To this end, the ski binding described in the second patent comprises an endpiece which is capable of upward pivotal displacement and which is carried by a body, the body being in turn rotatably mounted on a pivot which is perpendicular to the ski. This pivot has two flat faces which are oriented in opposite directions and against which are applied respectively a bearing surface formed in the end-wall of the rotary body and a piston mounted within the rotary body, a single spring being applied against the piston. The corresponding jaw unit is pivotally mounted directly on the rotary body of the ski binding about a transverse axis parallel to the top surface of the ski. However, the jaw unit is maintained in its normal position by a cross-pin interposed between the end-wall of the rotary body and the corresponding flat face of the pivot, the opposite ends of the cross-pin being adapted to cooperate with guide ramps provided on the jaw unit.
When this ski binding is employed as a toe-abutment device, the arrangement described in the foregoing produces a reduction in elastic resistance to torsion in the event of a backward fall of the skier, whereas a forward fall produces no such reduction. In actual practice, however, many of the falls experienced by skiers correspond to a complex movement of falling forward and twisting. When this occurs, it is essential to provide for a reduction in the resistance which acts in opposition to rotational displacement.
Furthermore, the arrangement provided in the ski binding considered is relatively complex, thereby imposing a heavy cost penalty.